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Biomedical subjects

K Nagata

Publications and source records attributed to K Nagata.

At least 235 records · Page 13Linked to original sources
PubMed1999

Gene expression of gastric type mucin (MUC5AC) in pancreatic tumors: its relationship with the biological behavior of the tumor.

Previously it has been found that the MUC2 gene for intestinal type secretory mucin is highly expressed in intraductal papillary mucinous tumors (IPMT), which are characterized by non-invasive growth and a favorable outcome. In contrast, MUC2 mRNA is rarely expressed in invasive ductal carcinomas (IDC), which have poor outcomes. The gastric type secretory mucin, MUC5AC, is strongly expressed in the surface mucous cells of gastric mucosa. As both MUC2 and MUC5AC mucins share the characteristics of forming highly viscous gels, it is expected that not only MUC2 mucin expression but also MUC5AC mucin expression may be associated with a favorable prognosis in patients with pancreatic tumors. MUC5AC mucin gene expression was examined in 24 cases of IPMT and 38 cases of IDC by in situ hybridization using a digoxigenin-labeled oligonucleotide. The results were compared with MUC2 mucin gene expression. Neither MUC5AC mRNA nor MUC2 mRNA was detected in normal pancreatic tissues. MUC5AC mRNA was expressed in 20 of 24 cases of IPMT (83%) and in five of 38 cases of IDC (13%). In contrast, MUC2 mRNA was expressed in 14 of 24 cases of IPMT (58%) and in none of the 38 cases of IDC (0%). The expression rates of MUC5AC mRNA and MUC2 mRNA in IPMT were significantly higher than those in IDC (P< 0.001, respectively). Intraductal papillary mucinous tumors are characterized by three histological types: (i) villous dark cell type; (ii) papillary clear cell type; and (iii) compact cell type. The villous dark cell type generally expressed both MUC5AC+ and MUC2+ genes. Alternatively, the papillary clear cell type and the compact cell type usually showed MUC5AC+ and MUC2- expression. Patients with MUC5AC mRNA expression had a significantly better survival prognosis than those with no MUC5AC mRNA expression (P< 0.005). In conclusion, MUC5AC gene expression occurs in a majority of IPMT cases, even in those with no MUC2 production. MUC5AC expression can be

Adenocarcinoma, Mucinous↗
PubMed1999

Spondylolysis at three sites in the same lumbar vertebra.

We report a rare case of spondylolysis that occurred at 3 sites in the fifth lumbar vertebra involving the bilateral pars interarticularis and the center of the right lamina. This is the first such case in the world literature.

Adolescent↗
PubMed1999

Knowledge, risk perception of AIDS and reported sexual behaviour among students in secondary schools and colleges in Tanzania.

A questionnaire survey was carried out among 1041 students in secondary schools and colleges in Dar-es-Salaam, Tanzania to evaluate the relationship between HIV-risky sexual behaviour and anti-condom bias, as well as with AIDS-related information, knowledge, perceptions and attitudes. Self-reportedly, 54% of students (75% of the boys and 40% of the girls) were sexually active, 39% had a regular sexual partner and 13% had multiple partners in the previous year. The condom use rate was higher than previous reports. However, 30% of sexually active respondents did not always use condoms (Risk-1 behaviour) and 35% of those with multiple partners in the previous year did not always use condoms (Risk-2 behaviour). Multiple logistic regression analyses indicated that 'sex partner hates condom' had association with both Risk-1 behaviour (OR 2.47; 95% CI 1.58-3.85) and Risk-2 behaviour (OR 2.47; 95% CI 1.10-5.48). 'Use of condom prevents HIV infection' also had association with both Risk-1 behaviour (OR 2.09; 95% CI 1.19-3.67) and Risk-2 behaviour (OR 3.73; 95% CI 1.28-11.03). Students engaging in risky behaviour were aware of the risk, even though they failed to change their behaviour. Reasons for the AIDS epidemic among Tanzanian students and the importance of more effective AIDS education are also discussed.

Adolescent↗
PubMed1999

Isolated recurrence of granulocytic sarcoma of the brain: successful treatment with surgical resection, intrathecal injection, irradiation and prophylactic systemic chemotherapy.

We describe a 40-year-old male who developed an isolated recurrence of granulocytic sarcoma (GS) of the brain 2 years following successful treatment of acute myeloblastic leukemia (AML; M2). Computed tomography (CT) scans and magnetic resonance (MR) images demonstrated a homogeneously enhanced tumor mass in the left temporal lobe and massive peritumoral edema. There was no evidence of relapse in the bone marrow. The patient underwent an emergency surgical resection of the tumor. Five courses of injection with cytarabine and prednisolone through an Ommaya reservoir and whole brain irradiation (total 40 Gy) were performed. Furthermore, prophylactic systemic chemotherapy with cytarabine and etoposide was added. He has been in complete remission for 21 months. Our results, together with other reported cases, indicate that a favorable outcome could be obtained by intensive and combined treatment for an isolated recurrence of GS of the brain if the bone marrow remained in complete remission.

Adult↗
PubMed1999

Characterization of a cb-type cytochrome c oxidase from Helicobacter pylori.

Helicobacter pylori is a microaerophilic Gram-negative spiral bacterium residing in human stomach. A cb-type cytochrome c oxidase that terminates the respiratory chain was purified to near homogeneity by solubilizing the membranes with Triton X-100 and applying anion exchange, Cu-chelating, and gel filtration chromatographies. Redox- and CO-difference spectra and pyridine ferrohaemochrome analysis showed the enzyme to contain three haems C, one low-spin protohaem, and one high-spin protohaem that probably forms a dioxygen-reducing bimetalic center with a copper atom. The enzyme actively oxidizes soluble cytochrome c from this bacterium (TNmax of about 250 s-1) with a Km of 0.9 microM. Yeast cytochrome c and N,N,N',N'-tetramethyl p-phenylenediamine (TMPD) are also oxidized at similar maximal velocities with larger Km's. Oxygen pulse experiments on resting cells in the presence of ascorbate plus TMPD or L-lactate indicated that this sole terminal oxidase pumps H+, although the H+ pumping activity by proteoliposomes reconstituted from the enzyme and P-lipids was low. Two main bands with haem C at 58 and 26 kDa were observed upon polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate and succeeding protein and haem staining. Sequencing of the operon encoding the subunits of the enzyme revealed the presence of ccoNOQP. N-terminal analysis of the 58 kDa band showed 15 or 13 amino acids coinciding with the amino acid sequences deduced from the DNA of ccoN and ccoO. CcoN, the largest subunit bearing two protohaems and copper, and ccoO, a mono-haem cytochrome subunit form a protein complex with an apparent molecular mass of 58 kDa, even in the presence of sodium dodecyl sulfate. The 26 kDa band is tentatively assumed to be ccoP with two haems C.

Amino Acid Sequence↗
PubMed1999

Subtilisin-like proprotein convertases, PACE4 and PC8, as well as furin, are endogenous proalbumin convertases in HepG2 cells.

Serum albumin is synthesized as a larger precursor form, proalbumin, which undergoes proteolytic processing at a dibasic site by a hepatic proprotein convertase within the secretory pathway to generate the mature form. Although furin, a member of the subtilisin-like proprotein convertase (SPC) family, was thought to be the only candidate hepatic convertase for proalbumin, SPC family members other than furin were recently suggested to also be involved in proalbumin processing. This study was designed to identify the endogenous proprotein convertases involved in proalbumin processing. Since human hepatoma HepG2 cells are highly differentiated and produce major plasma proteins, this cell line was used as a model for hepatocytes. Northern blot analysis revealed that PACE4, furin and PC8 of the SPC family were expressed in HepG2 cells as well as in the liver. Ribonuclease protection assay showed that PACE4A-II mRNA is the major transcript in HepG2 cells among the PACE4 isoforms. The coexpression studies showed that furin, PACE4A-II and PC8 were all able to convert proalbumin to albumin correctly. To elucidate the roles of these endogenous SPC family members in proalbumin processing, the antisense RNA for PACE4, furin and PC8 was stably expressed in HepG2 cells, respectively. The expression of each antisense RNA resulted in approximately 30% inhibition of endogenous proalbumin processing. We therefore concluded that PACE4 and PC8, as well as furin, are involved in the processing of proalbumin in HepG2 cells, and that these SPC family members are functionally redundant in this processing.

Furin↗
PubMed1999

Solution structure of the SH2 domain of Grb2/Ash complexed with EGF receptor-derived phosphotyrosine-containing peptide.

1H, 13C, and 15N NMR resonances of the SH2 domain of Grb2/Ash in both the free form and the form complexed with a phosphotyrosine-containing peptide derived from the EGF receptor were assigned by analysis of multi-dimensional, double- and triple-resonance NMR experiments. From the chemical shift changes of individual residues upon peptide binding, the binding site for the peptide was mapped on the structure of Grb2/Ash SH2. The peptide was not recognized by the groove formed by the BG and EF loops, suggesting that the EGFR peptide does not bind to Grb2/Ash SH2 in an extended conformation. This was supported by analysis of the binding affinity of mutants where residues on the BG and EF loops were changed to alanine. The present results are consistent with the recently reported structures of Grb2/Ash SH2 complexed with BCR-Abl and Shc-derived phosphotyrosine containing peptides, where the peptide forms a turn conformation. This shows that the specific conformation of the phosphotyrosine-containing sequence is required for the SH2 binding responsible for downstream signaling.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Enhancement of secretion of human procollagen I in mouse HSP47-expressing insect cells.

We previously demonstrated that insect cells were able to synthesize recombinant human procollagen I as triple-helical heterotrimers when transfected with cDNAs of both proalpha1(I) and proalpha2(I) chains. However, most of the heterotrimers were retained within the cells, unlike in the case of mammalian cells [Tomita, M., Kitajima, T., and Yoshizato, K. (1997) J. Biochem. 1061-1069]. In an attempt to improve the secretion of the heterotrimers, we introduced the putative collagen-specific chaperone HSP47 into this insect expression model. Mouse HSP47 produced by the insect cells bound intracellularly to both human proalpha1(I) and proalpha2(I) chains and enhanced the secretion of procollagen I heterotrimers. HSP47 was also coexpressed with either proalpha1(I) chains or proalpha2(I) chains, which showed that it enhanced the secretion of the former but not the latter. This selective effect of HSP47 was similarly observed in the cells treated with inhibitors of procollagen triple helix formation, indicating that HSP47 can also accelerate the secretion of non-helical procollagens. HSP47 did not change the intracellular solubility of proalpha1(I) and proalpha2(I) chains in 1% NP-40, eliminating the possibility that it prevents proalpha chains from aggregating into insoluble forms within the insect cells. We concluded that HSP47 can play a role in the secretion of alpha1(I)-procollagen chains in the insect cell model. The present study also demonstrated the dissimilarity in the mechanism of folding and secretion of the expressed procollagen I between the insect and mammalian cells.

Animals↗
PubMed1999

Unilateral Schamberg disease in a 14-year-old Japanese boy.

We report a 14-year-old Japanese boy who has had asymptomatic, multiple, reddish-brown macules and petechiae distributed segmentally only in the right lower extremity for the last 6 months. Histological examination showed a perivascular lymphohistiocytic infiltrate in the papillary dermis, extravasation of red blood cells, and hemosiderin deposition. Treatment with tranilast and topical corticosteroid was dramatically effective. Although the histological findings were compatible with those of Schamberg disease, this case was unusual because the patient was very young and only one extremity was affected.

Administration, Topical↗
PubMed1999

SCH 51344, an inhibitor of RAS/RAC-mediated cell morphology pathway.

RAS interacts with multiple targets in the cell and controls at least two signaling pathways, one regulating extracellular signal-regulated kinase (ERK) activation and the other controlling membrane ruffling formation. These two pathways appear to act synergistically to cause transformation. Human smooth muscle alpha-actin promoter is repressed in RAS-transformed cells and derepressed in revertant cell lines, suggesting that it is a sensitive marker to follow phenotypic changes in fibroblast cells. SCH 51344 is a pyrazoloquinoline derivative identified on the basis of its ability to derepress alpha-actin promoter in RAS-transformed cells. Previous studies have shown that SCH 51344 is a potent inhibitor of RAS transformation. However, SCH 51344 had very little effect on the activities of proteins in the ERK pathway, suggesting that it inhibits RAS transformation by a novel mechanism. Recently, we have demonstrated that SCH 51344 specifically blocks membrane ruffling induced by activated forms of H-RAS, K-RAS, N-RAS, and RAC. Treatment of fibroblast cells with this compound had very little effect on RAS-mediated activation of ERK and JUN kinase activities. SCH 51344 was effective in inhibiting the anchorage-independent growth of Rat-2 fibroblast cells transformed by the three forms of oncogenic RAS and RAC V12. These results indicate that SCH 51344 inhibits a critical component of the membrane ruffling pathway downstream from RAC and suggest that targeting this pathway may be an effective approach to inhibiting transformation by RAS and other oncogenes.

Actins↗
PubMed1999

Sperm chromatin decondensation by template activating factor I through direct interaction with basic proteins.

Template activating factor I (TAF-I) was originally identified as a host factor required for DNA replication and transcription of adenovirus genome complexed with viral basic proteins. Purified TAF-I was shown to bind to core histones and stimulate transcription from nucleosomal templates. Human TAF-I consists of two acidic proteins, TAF-Ialpha and TAF-Ibeta, which differ from each other only in their amino-terminal regions. Here, we report that TAF-I decondenses demembraned Xenopus sperm chromatin. Human TAF-Ibeta has a chromatin decondensation activity comparable to that of NAP-I, another histone binding protein, whereas TAF-Ialpha has only a weak activity. Analysis of molecular mechanisms underlying the chromatin decondensation by TAF-I revealed that TAF-I interacts directly with sperm basic proteins. Deletion of the TAF-I carboxyl-terminal acidic region abolishes the decondensation activity. Interestingly, the acidic region itself is not sufficient for decondensation, since an amino acid substitution mutant in the dimerization domain of TAF-I which has the intact acidic region does not support chromatin decondensation. We detected the beta form of TAF-I in Xenopus oocytes and eggs by immunoblotting, and the cloning of its cDNA led us to conclude that Xenopus TAF-Ibeta also decondenses sperm chromatin. These results suggest that TAF-I plays a role in remodeling higher-order chromatin structure as well as nucleosomal structure through direct interaction with chromatin basic proteins.

Amino Acid Sequence↗
PubMed1999

Cloning and functional expression of an SGLT-1-like protein from the Xenopus laevis intestine.

A cDNA encoding an Na+-glucose cotransporter type 1 (SGLT-1)-like protein was cloned from the Xenopus laevis intestine by the 5'- and 3'-rapid amplification of cDNA ends method. The deduced amino acid sequence was 673 residues long, with a predicted mass of 74.1 kDa and 52-53% identity to mammalian SGLT-1s. This gene was expressed in the small intestine and kidney, reflecting a tissue distribution similar to that of SGLT-1. The function of the protein was studied using the two-microelectrode voltage-clamp technique after injection of cRNA into Xenopus laevis oocytes. Perfusion with myo-inositol elicited about twofold larger inward currents than perfusion with D-glucose. The order of the substrate specificity was myo-inositol > D-glucose > D-galactose >/= alpha-methyl-D-glucoside. The current induced by myo-inositol increased with membrane hyperpolarization and depended on external myo-inositol and Na+: the apparent Michaelis-Menten constant was 0.25 +/- 0.07 (SD) mM with myo-inositol, whereas the apparent concentration for half-maximal activation was 12.5 +/- 1.0 mM and the Hill coefficient was 1.6 +/- 0.1 with Na+. In conclusion, the cloned protein shares features with both SGLT-1 and the Na+-myo-inositol cotransporter.

Amino Acid Sequence↗
PubMed1999

Development of sleep spindles in young children and adolescents.

The development of sleep spindles was studied quantitatively in 32 healthy subjects between the ages of 4 and 24 years. The peak frequency distribution of the spindles showed a bimodal pattern with 11.0 to 12.75 Hz in the frontal area and 12.5 to 14.5 Hz in the centroparietal area. The two types of spindle activity showed different courses of maturation. The peak frequency of the centroparietal spindles gradually increased linearly with age, whereas the frontal spindles abruptly increased in frequency during early adolescence. Regarding the power spectra, while centroparietal spindles showed little change in power from 4 to 24 years of age, frontal spindles decreased remarkably in power and became stable at about 13 years of age. The two types of spindles and the difference in their development may suggest the existence of different generators or a topographical difference during maturation in the thalamocortical network. The frontal spindle activity could be a good indicator to evaluate CNS maturation in young children and adolescents.

Adolescent↗
PubMed1999

Clinical aspects of the "third rhythm" of the temporal lobe.

We studied clinical aspects of the "third rhythm," which was first described by Niedermeyer as alpha-like activity of the temporal lobe. By scalp EEG, temporal alpha-like activity was recorded in 15 (0.30%) of 4929 patients over 20 years of age. The temporal alpha-like activity was observed in 5 patients who had clinical and brain imaging findings indicating the presence of a cerebrovascular disorder. The alpha-like rhythm of these patients was left-sided, and wicket spikes appeared in the same region as the alpha-like rhythms in 4 of the 5 patients. In 8 of the 15, the temporal alpha-like rhythm was recorded over the defective bone or replacement bone after intracranial surgery. The alpha-like rhythm of these patients was similar to breach rhythm in the temporal region. The remaining 2 patients had not undergone intracranial surgery nor did they show symptoms of cerebrovascular disorders. The temporal alpha-like rhythms in one of these 2 might be a physiological third rhythm detected by scalp EEG through congenital bone thinning. Our observation supports the existence of intrinsic activity of the temporal lobe (the third rhythm). The third rhythm can be recorded by routine scalp EEG in some clinical conditions, and it is important to recognize this rhythm when one encounters temporal rhythmic activity independent of alpha rhythm of the occipital lobe.

Adult↗
PubMed1999

Effect of HSP47 on prolyl 4-hydroxylation of collagen model peptides.

Prolyl 4-hydroxylation, the most important post-translational modification in collagen biosynthesis, is catalyzed by prolyl 4-hydroxylase, an endoplasmic reticulum-resident enzyme. HSP47 is a collagen-binding stress protein which also resides in the endoplasmic reticulum (Nagata, K. and Yamada, K.M. (1986) J. Biol. Chem., 261, 7531-7536). Both prolyl 4-hydroxylase and HSP47 interact with procollagen alpha-chains during their folding and/or modification in the endoplasmic reticulum. Recent study has revealed that a simple collagen model peptide, (Pro-Pro-Gly)n, is recognized by HSP47 as well as by prolyl 4-hydroxylase in vitro (Koide et al., manuscript submitted). In the present study, we investigated the effect of HSP47 on the prolyl 4-hydroxylation of such collagen model peptides. To monitor the enzymatic hydroxylation of the peptides, we developed a non-RI assay system based on reversed-phase HPLC. When HSP47 was added to the reaction mixture, substrate and less-hydroxylated materials accumulated. This effect depended on the peptide-binding activity of HSP47, because a mutant HSP47 without collagen-binding activity did not show any inhibitory effect on prolyl 4-hydroxylation. Kinetic analysis and other biochemical analyses suggest that HSP47 retards the enzymatic reaction competing for the substrate peptide.

Animals↗
PubMed1999

Enzymatic characterization of human cytosolic sulfotransferases; identification of ST1B2 as a thyroid hormone sulfotransferase.

Sulfotransferases (ST) are contained as multiple forms in human tissues with overlapping substrate specificities. To identify a form which contributes to the metabolism of 3, 3',5-triiodothyronine (T3), the functional properties of human STs were compared using recombinant STs, ST1A3, ST1A5, ST1B2, ST1E4 and ST2A3. ST1B2 showed a high affinity (Km 46.2 microM) for T3 sulfation, whereas ST1A3, ST1A5, ST1E4 and ST2A3 showed high affinities to p-nitrophenol (Km 0.4 microM), dopamine (Km 7.1 microM), beta-estradiol (Km 0.3 microM) and dehydroepiandrosterone (Km 3.3 microM), respectively. In Western blotting using antibodies raised against an individual ST, hepatic absolute amounts of these STs were determined. The content of ST1B2 in human liver correlated well with T3 sulfation activities in human liver (r=0.96). These results indicate that ST1B2 is biochemically distinct from other forms of ST, and is involved in the metabolism of T3 in human. In addition, studies of thermal stability and 2,6-dichloro-4-nitrophenol (DCNP) inhibition showed that ST1B2 was thermostable and more DCNP resistant than other forms of ST. Affinities for a co-factor, phosphoadenosine 5'-phosphosulfate, also differed 9-fold among 5 different forms of ST.

Cytosol↗
PubMed1999

Expression of cytokine and adhesion molecule mRNA in atherectomy specimens from patients with coronary artery disease.

Coronary arteriosclerosis is an underlying condition in acute myocardial infarction (AMI), unstable angina pectoris (UAP) and stable angina pectoris (SAP), and is also related to restenosis (RS) following coronary intervention. To investigate the pathogenesis of this condition, a quantitative reverse transcriptase polymerase chain reaction was used to determine relative levels of mRNA for interleukin (IL)-1beta, IL-6, IL-8, transforming growth factor beta (TGF-beta), intercellular adhesion molecule (ICAM)-1, E-selectin and vascular cell adhesion molecule (VCAM)-1 using directional coronary atherectomy (DCA) specimens. Eleven patients with AMI, 7 with UAP, 10 with SAP and 6 with RS following a previous coronary intervention underwent DCA. The mRNA intensity for each molecule was expressed by comparing it with that of beta-actin mRNA. The AMI and UAP patients showed high frequencies of mRNA for IL-1beta, IL-8, TGF-beta, and ICAM-1 together with strong intensities of expression, whereas SAP patients showed decreased mRNA expression for these molecules. Increased IL-6 mRNA expression was observed only in AMI samples. Specimens from RS patients revealed an accumulated expression of proinflammatory cytokines, except for IL-6, as well as of TGF-beta. The study suggests that variation in mRNA expression may reflect the pathophysiology of specific types of coronary artery disease, and remodeling following vascular injury.

Aged↗